Aircraft ground maintenance tether assembly

ABSTRACT

A ground maintenance assembly for an aircraft generally including a support member provided with a longitudinal bore and a rigid post portion, a first inner member provided with a longitudinal bore disposed in and secured in such support member and a second inner member provided with a longitudinal recess adapted to receive a pitot tube of such aircraft.

RELATED APPLICATION

This application is a continuation-in-part application of U.S. Ser. No.13/153,553, filed on Jun. 6, 2011.

FIELD OF THE INVENTION

The present invention relates to the ground maintenance of aircraft and,in particular, to a tether assembly for assuring removal of groundprotective devices prior to flight.

BACKGROUND OF THE INVENTION

During extended ground maintenance times, various protective devices arecommonly installed to prevent damage to instrumentation and/orstructural damage to the aircraft. Representative are pitot tube coversand landing gear locks pins.

Pitot tubes are used on aircraft for measuring speed and altitude. Theyare sensitive and delicate, and thus prone to damage during maintenance,and storage. To limit damage and contamination, the pitot tube coversare installed during any appreciable outdoor layover to prevent dust,particulates, water, and other foreign matter from entering the probeports, all of which can contribute to erroneous outputs. Equallyimportant to installation during layover is the need to remove the pitottube covers prior to flight. Should they remain in place during flight,there are no effective procedures for removal and the instrument'sassessment of speed and altitude are severely compromised. Accordinglyand, as a matter of standard operating procedure, if not removed theplane must return to base for cover removal. Inasmuch as the plane mayhave departed with a full fuel load, landing under such high loadingconditions can create substantial forces that can damage the airframe orotherwise affect structural integrity. It would therefor be desirable toprovide an apparatus and procedure for assuring the removal of pitotcovers prior to flight.

It is also desirable to provide the pitot covers and installationequipment in a package that can be carried on the associated plane, thusenabling aircraft, such as military, commercial or business planes, thatare transient between facilities of varying ground maintenancecapabilities, to have assured access to the covers regardless of landinglocation. It is also desirable to limit the number of separate items onany maintenance package. Thus installation equipment such asinstallation poles for higher mounted pitot tubes may be necessary andunavailable at remote locations but present an additional piece ofequipment that must. It would thus be further desirable to integrateinstallation equipment in an assembly that could be readily stowed onand transported with the aircraft. On many aircraft, the covers may bemanually installed without auxiliary equipment. On other aircraft, theprobes are just out of reach and require installation tools. For largeraircraft with higher mounted probes, an installation tool such asdisclosed in our pending application, U.S. Ser. No. 12/580,234 filed onOct. 15, 2009, provides effective installation assistance. The tool,however, is considered too bulky for aircraft transport, and isgenerally conveniently available at facilities able to handle the largeraircraft.

The landing gear lock pins are installed to disable the landing gearretracting system to prevent inadvertent actuation during maintenanceand/or ground operations that could collapse the nose wheel andstructurally damage the aircraft. As with the pitot tube covers, thepins must be removed prior to flight, and if not removed, the plane mustreturn to base with the resultant unnecessary expense and potentialstructural damage from a full weight landing.

While there are established procedures for removing the covers and lockpins, human error nonetheless continues to produce non-compliantflights. Accordingly, it would be desirable to provide a maintenanceproduct that would further reduce the chances of the covers and lockpins remaining on the aircraft at takeoff.

SUMMARY OF THE INVENTION

The present invention provides a highly visible tether assembly for useon parked aircraft that interconnects the pitot tube covers with thelanding gear lock pin thereby assuring removal of both the covers andthe lock pin as part of the aircraft preflight check list. The assemblyis made of heat and environment resistant materials that avoidinstrument and air craft damage during installation and residence. Forlower mounted probes, the tether connects directly with the covers. Forhigher mounted probes, the tether attaches to pole mounted covers.

More particularly, the tethering assembly comprises a plurality of pitottube covers for preferably all of the aircraft's pitot tubes, on bothsides of the aircraft, which are interconnected by a lanyard oftemperature resistant woven aramid material wherein the lanyard isprovided with a middle biasing sleeve that elastically conforms to thefuselage contour in installation. The sleeve includes a connecting strapcarrying a lock pin at an outer end that for disabling the landing gearretraction assembly to prevent inadvertent actuation on the ground.

In one aspect, the invention provides a ground maintenance assembly foran aircraft having at least a pitot tube on opposed sides of a fuselageabove a front landing gear having a retracting linkage immobilized byinsertion of a locking pin into a locking aperture thereon wherein themaintenance assembly includes a pitot tube cover for telescopicinsertion over each pitot tube; an expandable tether assembly havingopposed elongated straps, each having a distal end connected to one ofsaid pitot tube covers, said tether assembly having a sleeve member witha passage therein, wherein one of said straps has a proximal end fixedlyconnected to said sleeve member and wherein the other strap has aproximal end connected to first end of an elastic member carried in saidpassage, said elastic member having a second end connected to saidsleeve member whereby the length of the tether assembly is less that thedistance about the fuselage between the pitot tubes and in assembly theelastic member is stretched to provide a biasing of the tether assemblyagainst the fuselage; and a connecting strap having a first end attachedto said tether assembly and a second end connected to said locking pin,said connecting strap having sufficient length in assembly to enableinsertion of said locking pin in said locking aperture. In otheraspects, the ground maintenance assembly may also use as the sleevemember is a planar rectangular sheet having opposed longitudinal edgesreleasably secured by fastening members to form a generally tubularshape with said passage extending therethrough. The ground maintenanceassembly may have the straps and said sleeve member formed of a heat andenvironment resistant woven material, such as a meta-aramid polymer. Theelastic member of the ground maintenance assembly may be an elastomersubject to ultraviolet degradation upon exposure to ambient sunlitconditions wherein the elastic member in said sleeve assembly isshielded from said condition in said passage. The ground maintenanceassembly may include banners carrying notifications for removal beforeaircraft flight are attached at plural locations on said covers and/ortether assembly.

In another aspect, the invention provides ground maintenance assemblyfor an aircraft having at least a pitot tube located on opposed sides ofa fuselage at an elevation above manual access and a front landing gearhaving a retracting linkage immobilized by insertion of a locking pininto a locking aperture thereon, said maintenance assembly comprising: apair of pitot cover pole assemblies, each comprising a pitot tube coverfor telescopic insertion over each pitot tube; an elastomeric bodycomprised of a matrix of fused milled rubber and heat resistant fiber,said body having a longitudinal bore; a tubular member of heat resistantwoven material bonded to an inwardly facing surface of said bore with asilicone adhesive, said tubular member telescopically receiving saidcover and being connected thereto; a spacer member as shown in U.S. Pat.No. 6,901,793 having one end connected to said elastomeric body and aconnecting member at another end; an expandable tether assembly havingopposed elongated straps, each having a distal end connected to one ofsaid connecting members of a pole assembly.

In a further aspect, the invention provides A pitot tube cover assemblyfor covering the pitot tube of an aircraft wherein said pitot tube islocated at an elevation beyond manual access, comprising: a pitot tubecover formed of a heat resistant woven material and having an open endedcavity for telescopically receiving the pitot tube; a cylindricalelastomeric support collar consisting of a matrix of cured rubber andheat resistant fiber, said sleeve having an axial bore therethrough; atubular sleeve of heat resistant woven material telescopically receivedin said bore and bonded to said support sleeve with a two part siliconerubber adhesive; an elongated shaft having first end connected to saidsupport collar whereby said shaft may be manually directed fortelescopically inserting said pitot cover over the pitot tube. Theassembly may have a tubular arm radially extending from an outer surfaceof the support collar and having an outwardly opening recess forreceiving said first end of said shaft, and may have a connecting memberis connected with a second end of said shaft, said connecting memberincluding a restraining device for holding the shaft in operativeposition on the aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become apparent upon reading the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is side view of an aircraft provided with an aircraft groundmaintenance tether assembly in accordance with an embodiment of theinvention;

FIG. 2 is a front view of the aircraft of FIG. 1;

FIG. 3 is a top view of the tether assembly;

FIG. 4 is a top view of the sleeve assembly for the tether assembly;

FIG. 5 is a view taken along line 5-5 of FIG. 4;

FIG. 6 is a schematic view of a landing gear assembly disabled by thelock pin of the tether assembly;

FIG. 7 is a side view of a pitot cover pole assembly for a tetherassembly in accordance with another embodiment of the invention;

FIG. 8 is a side cross sectional view of the pitot cover pole assemblyof FIG. 7 installed over the pitot tube of an aircraft;

FIG. 9 is a fragmentary cross sectional view of pitot cover supportsleeve; and

FIG. 10 is a cross sectional view of the pitot cover assembly in themanufacturing mold.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to drawings, FIGS. 1 and 2 show an aircraft ground maintenancetether assembly 10 for assuring the installation and removal of coversfor the pitot tubes 14 of an aircraft 16 during ground stays formaintenance, layovers and other normal extended aircraft ground basedactivities. The tether assembly 10 has particular benefit for theHercules C130 aircraft. Therein, the aircraft 16 is provided with a pairof vertically spaced pitot tubes 14 on each side of the aircraft,generally vertically positioned above the front landing gear 20. Asdescribed below, the tether assembly 10 also includes a lock pin forconventional insertion into an aircraft dependent aperture in the frontlanding gear retraction assembly for disabling the retraction systemtherefor in order to avoid inadvertent collapse during ground operation.As part of the preflight check list, the pitot tube covers are removedand the lock pin is removed whereby retraction mechanism is againenabled.

The tether assembly 10 of the present invention integrates a tetheringsystem with both the pitot covers and the locking pin to assure removalof both items prior to flight. Referring to FIGS. 3 through 5, thetether assembly 10 includes an expandable sleeve assembly 30 havingstraps 32, 34 with proximal ends extending from opposite ends thereofand distal ends attached to a pitot tube cover assembly 36, eachcomprising a pair of pitot covers 38 a and 38 b interconnected byconnecting strap 40. A lock pin strap 42 has an end loop 44 encirclingthe center section of the sleeve assembly 30 and terminates with acarrying ring 46 threaded through a cross hole in the head section 48 ofa landing gear lock pin 50. The lock pin 50 includes a shank section 52for coupling with the landing gear retraction system as described belowto prevent inadvertent actuation of the retraction system during groundoperations. A retaining strap 54 is connected to the cover assembly 32and retains the strap 42 in assembly.

Referring to FIGS. 4 and 5, the sleeve assembly 30 comprises arectangular body panel 60 having a base surface 61 connected to areversely turned face surface 62. The base surface 61 has a reverselyfolder flap 63, The flap 63 and face surface 62 have a longitudinalfastening system 64, such as hook and loop strips, at the lateral sidesthereof for forming a sleeve with a longitudinal passage 66therethrough. Other systems such as zippers, button, snaps or the likecan be used for the sleeve and to permit access to the interior forassembly and repair. The strap 32 is fixedly attached to the panel 62 bycross stitching 64. The strap 34 is attached to the panel 62 by anelastic cord assembly 66. The cord assembly 66 includes end loops 70connected at outer ends to the straps 32, 34, respectively, andconnected at inner ends to end loops 74 of an elastic cord 78. Theentire cord assembly 66, particularly the elastic cord 78, is retainedinterior of the cover assembly 60 and thus shielded from environmentallydegrading UV radiation. Normally, these cords are susceptible toenvironmental degradation during the long layover times the aircraft mayexperience, and consequently fail and require replacing. By retainingthe cord entirely in the passage, the cord in isolated from sunlitconditions, extending the trouble free life thereof. The cord comprisesan elastomeric core covered by an outer fabric sleeve. A bungee typecord is a preferred cord construction.

Accordingly, the length of the assembly may be elastically elongated inlength in the direction of the arrows to provide tensioning of thetether assembly against the fuselage of the aircraft in assembly.

Each cover assembly 36 includes one or more pitot covers 38 connected toa distal end of the strap. For the present embodiment two covers areprovided, a lower cover 38 a and an upper cover 38 b. Both covers areprovided with diametrically opposed side loops 74. One loop of eachlower cover 38 a is connected to the distal ends of the straps 32, 34.An opposed loop of the lower cover is connected the connecting strap 40connected to a comparable loop on the upper cover. Each cover may havean additional loop for mounting a highly visible removal banner 80thereon carrying an appropriate indicia thereof such as “Remove BeforeFlight” reinforcing notice for removal prior to flight. Suitable coversare described in our prior patents, U.S. Pat. Nos. 6,412,343 and6,901,793. Such covers are commercially available from SesameTechnologies Inc. of Belhaven, N.C., exclusive licensee of the abovepatents. Preferably, the covers are formed of heat and abrasionresistant woven materials such as meta-aramid polymers. Suitablematerials are available such as NOMEX™ or KEVLAR™ materials from E. I.DuPont deNemours and Company.

In the present embodiment, the pitot tubes are at an elevation thatmanual positioning of the covers on the pitot tubes is required.

The length of the connecting strap 40 is preferably slightly longer thanthe distance between the pitot tubes to avoid imposing any adverseloading thereon. The overall length of the tether assembly with respectto the first or lower pitot tube covers is slightly less than thedistance from the associated pitot tubes about the fuselage, so as toresult in an elastic biasing from the cord to retain the tether assemblysnugly against the aircraft, notwithstanding ambient wind conditions,without imparting significant loading on the pitot tubes. The connectingstrap 42 and the lock pin 50 have a length allowing insertion of thelock pin without strap tensioning, but short enough so as not to becomeentangled with any neighboring components.

The landing gear disabling takes various forms dependent on theaircraft, mechanically preventing actuation of a retraction linkage orby disabling a retraction actuator. In these designs, a lock pin isinserted into the appropriate aperture. By way of example and notlimitation, referring to FIG. 6, the front landing gear retractionassembly 90 is provided with aligned through holes in the gear struts92, 94. The shank 52 of the lock pin 50 is inserted into the holes andprevents articulation of the struts thereby disabling the retractionsystem and maintaining the lowered position of the gear.

For installation, the covers are installed alternately at the sides ofthe aircraft thereby tensioning the cover assembly to provide thebiasing of the tether assembly against the fuselage. Thereafter the lockpin in installed. Removal is by reverse sequence. By coupling thelanding gear locking pin and covers in a single assembly with highlyvisible banners and covers. The identification of one component is anindication that preflight removal has not been completed. Thereafter,undertaking the removal of one component is physically coupled toadjacent components thus compelling the ground personnel to remove allitems in order to stow the assembly prior to flight. Also, the wovenfabric construction of the major components of the tether assembly lendsto compact storage on the aircraft thus providing an assured deployablemaintenance assembly at the next required layover.

In the embodiment shown in FIGS. 7-10, the tether assembly 110 isadapted for manual installation of the pitot tube covers on pitot probesthat are positioned at an elevation above manual access. Therein, apitot cover pole assembly 112 allows manual positioning and installingof the covers at the higher elevation, while providing integration in atether assembly for unitized deployment and storage, or without thetether, and allowing singular disposition, transport, and/or storage. Inthe latter condition, the end of the cover assembly is provided with aconnecting member for attaching to an aircraft surface to restrictmovement during deployment.

Referring to FIGS. 7 and 8, the cover pole assembly 112 comprises anelastomeric heat resistant support sleeve 120 carrying a heat resistantwoven support tube 122 holding a pitot over 124, a rigid support post126 connected to the sleeve 120 and a connector arm 128 attached at thebottom end of the support post 126. The connector arm 128 is connectedto one end of a tether assembly 129 as described above, the other end ofthe tether assembly 129 connected with a cover assembly for the pitotprobe(s) on the other side of the aircraft.

The support sleeve 120 comprises an elastomeric cylindrical body 130having a longitudinal bore therethrough. The body 130 includes anintegral connecting arm 132 extending radially downward from the outersurface of the body 130. The arm 132 includes a downwardly openingrecess 134 for receiving in assembly a terminal end of the support post126.

The support tube 122 is a woven cylindrical sleeve of a heat resistantmaterial such as Kevlar having a diameter about the same as the bore ofthe support body 130. The body 130 is a cured matrix of milled rubberand heat resistant fibers, preferably the same material as the sleeve.As such, the body does not bind adequately directly to the woven tube.Referring to FIG. 9, we have found that pretreating the woven tube 128with a two part silicone rubber 140 will provide a tightly bondedinterface with the body matrix.

Referring additionally to FIG. 10, this is accomplished by placing thewoven tube 128 over a cylindrical core mandrel 144 and applying a layerof the silicone rubber 140 about the tube and through the weave toestablish to establish coating layers on the inner and outer surfaces ofthe tube. The ends of the tube are reversely tucked into the mandrelbore to form the tube mandrel assembly 148. A suitable silicone rubberis a two part silicone package from Wack Chemie AG comprising Part A asproduct no. 3009-28 and Part B as product no. 3009-20B.

As shown in FIG. 10, the tube/mandrel assembly 148 is mounted in a threepiece mold 150 comprising a split two-piece center section 152 havinginterior surfaces corresponding to the outer surfaces of the supportsleeve 120, and end caps 154 having inner hubs 156 supporting thetube/mandrel assembly 148 and providing the end surfaces of the sleeve.A side core 158 is provided for establishing the recess for the supportpost.

The mold halves of the center section are packed with the milled uncuredrubber and fiber mixture and manually distributed to the desiredcontours for the support sleeve. A high temperature silicone rubber issheet form is milled with loose, chopped fiber fines to form a matrix ofabout 1-2% fiber by weight. The fibers are preferably the heat resistantfibers used in the covers, such as Kevlar. A suitable uncured rubber isa 70 durometer rubber available as product no. 25787-V-Red fromSilcotech North America, Inc. The matrix is processed into thin sheetsfor conformal insertion into the mold.

With the mandrel assembly and side core roughly positioned, the moldhalves are assembled and clamped. The mold assembly is heated at atemperature and for a time sufficient to cure the matrix. Temperaturesin the range of about 350° F. to 400° F. for a period of about 10 to 20minutes have provided satisfactory results.

After curing, the part is disassembled from the mold components, theends of the sleeve removed from the mandrel, and the mandrel removed.The sleeve ends are inwardly folded as shown in FIG. 8 to form outerannuli 164 with aligned openings. A pitot cover 124 is then insertedinto the annuli, which are circumferentially attached thereto bystitchings 168, 169. The pitot cover 124 is of the type disclosed inU.S. Pat. No. 6,901,793. Other suitable covers are commerciallyavailable from Sesame Technologies, Inc. The cover 124 on the forwardend 170 includes an annular sealing element 172 that is telescopicallyinserted over the frontal end 174 of the pitot probe 176 is inserted.The rearward end 178 of the cover is folded and stitched for form aclosure. A banner 180 containing conventional indicia such as “RemoveBefore Flight” is attached to the rearward end 178.

The support post 126 is formed of a relatively rigid but limitedlyflexible heat resistant material such a fiberglass. The ends of the post126 are inserted into recesses in the support body and the connector arm128 and attached thereat by a suitable adhesive. The connector arm 128is preferably molded from the said material as the support collar toprovide a flexible, durable and soft material to avoid any impact orabrasion damage to the fuselage during deployment. For additionalresistance to separation, the post ends may be connected to theassociated part by cross members 182, such a rigid pin, or by flexiblelashing. The connector arm 128 includes an end aperture 184 forconnection with the tether 129 or mechanical attachment to the aircraft.The arms and support post may be clad by heat shrink tubing 184 toprovide exterior protection and to unitize the assembly of the supportpost assembly.

For aircraft installation, the cover assemblies may be attached to atethering assembly as described above, before or after installation overthe pitot probes. If after installation, it is preferred to incorporatea decoupling component such as clip at both ends to facilitateinterconnection and separation. While extended lengths of support postmay be used, it is generally preferred to limit the length to about 1-2feet, depending on the aircraft being serviced. For instance, a 12 inchpost has been demonstrated as sufficient for the expected range ofpersonnel on military aircraft such as, without limitation, the C130H,commercial aircraft such as the Boeing 737, and business aircraft suchas Challenger and Gulfstream planes. Higher elevation probes arepreferably handled by specialized installation tools such as theinstaller described in out pending application, U.S. Ser. No. 12/580,234filed on Oct. 15, 2009 and entitled “PITOT TUBE COVER INSTALLATIONTOOL”.

Having thus described a presently preferred embodiment of the presentinvention, it will now be appreciated that the objects of the inventionhave been fully achieved, and it will be understood by those skilled inthe art that many changes in construction and widely differingembodiments and applications of the invention will suggest themselveswithout departing from the sprit and scope of the present invention. Thedisclosures and description herein are intended to be illustrative andare not in any sense limiting of the invention, which is defined solelyin accordance with the following claims.

What is claimed is:
 1. A ground maintenance assembly for an aircrafthaving at least one pitot tube located on a side of the fuselage thereofat an elevation above manual reach and a front landing gear having aretractable linkage immobilized by insertion of a locking pin into anaperture therein, comprising: a support member having a longitudinalbore therethrough and a rigid post disposed at an angle to said bore; afirst inner member formed of a heat resistrant woven material having alongitudinal bore therethrough, disposed in the bore of said supportmember and secured thereto; and a second inner member disposed in andsecured to said first inner member, formed of a heat resistant wovenmaterial and provided with a longitudinal recess for receiving a pitottube therein upon manipulation of said post portion of said supportmember.
 2. An assembly according to claim 1 including a tether assemblyto which said post portion is connected.
 3. An assembly according toclaim 2 wherein said tether assembly includes a pin insertable in saidaperature of said retractable linkage of said landing gear.
 4. Anassembly according to claim 1 including a pair of said assemblies,including a pair of said support members, each attached to spaced endsof a tether assembly.
 5. An assembly according to claim 4 wherein saidtether assembly includes a pin insertable in said aperature of saidretractable linkage of said landing gear.
 6. An assembly according toclaim 1 wherein said support member and said post portion thereof areformed of a relatively rigid but flexible heat resistant material.
 7. Anassembly according to claim 1 wherein said support member and said postportion thereof are formed of fiberglass.
 8. An assembly according toclaim 1 wherein said second inner member includes an annular sealingelement engageable by said pitot tube upon receipt of said pilot tubeinto the recess of said second inner member.